Answer:
12.6
Step-by-step explanation:
If 21 divided by 5 is 4.2, you should multiply 3 by 4.2 you'll then get 12.6. to double check, do 5 divided by 3, which is 1.67, and 21 divided by 12.6 is also 1.67. so side OP is 12.6! :)
A . a perpendicular bisector
Answer:
35/72 
Step-by-step explanation:
Rectangle Formula: 
Switch the variables with the numbers given:

Multiply the top and bottom:
5*7 = 35
9*8 = 72
35/72 = Area
Answer:
15 in
Step-by-step explanation:
(basexheight)/2=area
basex6=45x2
base=45/3
base=15